


Learning Curves

by Kestrealbird



Category: Fate/stay night & Related Fandoms
Genre: (Cu voice) respect Diarmuid or die by my hand, Cu is very sweet and caring, Diarmuid puts up with things he shouldnt, Gen, M/M, Pre-Relationship, and I'm fixing that, mood tbh, these two are slept on as a pair, this is shorter than i intended but i like the vibes so
Language: English
Status: Completed
Published: 2020-09-26
Updated: 2020-09-26
Packaged: 2021-03-07 17:55:27
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 1,422
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/26661787
Author URL: https://archiveofourown.org/users/Kestrealbird/pseuds/Kestrealbird
Summary: “Stop pacing before you leave a groove in the earth.”“Stop pacing,” Caster mocks, hitting his back loudly against a tree as if to say, see? Not pacing. Happy now? “Told you not to come here,” he scowls.Saber can’t see the scowl but he can hear it well enough.
Relationships: Cú Chulainn | Caster/Diarmuid Ua Duibhne | Saber
Comments: 6
Kudos: 20





	Learning Curves

**Author's Note:**

> Sabermuid x CasCu is fucking godtier and if I have to fill the tag myself than by god I will

Caster follows Saber from the White Swan Tavern, heedless of Saber’s repeated assurances that he’ll be fine by himself, really, it happens all the time. It’s all bullshit, is what Caster thinks. Says as much too, less with words and more with the fire dancing on his fingertips, bright and burning and _angry._

It’s flattering, Saber supposes, that someone cares enough to start a tavern brawl to defend his place in the world. Unnecessary, but flattering all the same.

Their campfire is still mostly intact from last night and Saber stretches out on his back on one of the logs, his ankle resting on his opposing knee, one arm resting across his stomach. Caster lights up the fire with enough force that Saber knows he’s doing it more for the sake of burning something than because either of them really need it.

“It’s fine,” Saber says for what feels like the hundredth time that night.

“No,” Caster snaps, “it really fucking isn’t.” 

For someone who walks around barefooted, he sure is making a lot of noise in the grass. Mostly stomping noises, interlaced with enough ferocious cursing that Saber wonders if he actually _is_ casting a plague on the towns folk’s houses like he’d threatened to earlier when Saber had hoisted him over his shoulder so he couldn’t punch someone's teeth out.

“No,” Saber agrees, “but it’s something I’ve learned to live with, so.” He shrugs a shoulder, keeping his eyes closed so he doesn’t have to actually _look_ at Caster’s pacing.

They’d known what they were getting into from the start, is the thing. Da Vinci and Dr Archaman had been reluctant to send anyone down here, knowing how viciously the humans in this time period tended to react to creatures like himself. It takes a Fae to hunt a Fae, though, and so Saber, after hearing the problem directly - and being reassured, _repeatedly,_ that they wouldn’t force him to do anything, which was preposterous, really, as if he could be _forced_ at all - had agreed to come down here himself and offer his own personal experience and insight to figure out who - and _what_ \- amongst his kind has been causing all the fuss.

Caster _hadn’t_ agreed, until Saber had jokingly asked if he’d like to play bodyguard and. Well. Here they are, he supposed.

It was just their luck that the moment they rayshifted here they’d just _happened_ to lose all signs of whatever Fae they were meant to be hunting. Normally he might find that amusing if it wasn’t so fucking irritating dealing with iron over every goddamn door.

 _Humans,_ really.

“Stop pacing before you leave a groove in the earth.”

“ _Stop pacing,_ ” Caster mocks, hitting his back loudly against a tree as if to say, _see? Not pacing. Happy now?_ “Told you not to come here,” he scowls. 

Saber can’t _see_ the scowl but he can hear it well enough. 

“You did. And I told you not to cause a scene.”

“I didn’t. _They’re_ the ones who made it an issue.”

Saber sighs through his nose, counts to ten and, when Caster’s anger still hasn’t settled, forces himself to sit up. “You already knew they would. Doesn’t mean you had to make it worse by trying to gouge someone's eyes out.”

“Deserved worse than that,” Caster says, and the runes currently passing between his fingers clack together ominously, as if he’s playing with chemicals that are two seconds away from mixing and choking everything within a thirty mile radius to death. 

_“Cú Chulainn._ ”

“Oh so now you use my name?”

“Don’t change the conversation,” he frowns.

“I’m not,” Caster says. “Just making an observation.” His eyes finally make contact with Saber’s own and he shivers under the bright red gaze. For all of Caster’s laid back lifestyle, his eyes are more than capable of pinning you to the spot like a butterfly on a wall and dissecting you into bite-sized pieces. For all that he looks human, his eyes are proof enough that he isn’t, and Saber’s not just talking about the rings.

“It’s not like you’ve ever given me permission to use it,” he mutters, distracted by the way the light catches on Caster’s eyes, turning them into a myriad of different shades. 

Caster huff's. “ _Fairies,_ ” he says, rolling his eyes. 

“Fae,” Saber corrects absently, watching curiously as Caster finally makes his way over to Saber’s side of the fire, sitting cross-legged right in front of him. The log gives Saber some height over him and it’s strange to look down at him from this angle, so Saber slides down to sit on the grass as well and almost immediately gets a hand shoved into his face.

Caster raises a brow and it takes Saber a second to realize what he’s waiting for. 

“...Are you serious?”

“Yes.”

 _Of course he is._ With great reluctance, Saber takes his hand and feels his veins thrum with promise. It’s always a heady feeling; try as he might he can never completely ignore it, and he’s certain that his pupils have dilated as a result, that he has a slightly manic look to himself. If Caster is at all concerned about this, he doesn’t show it, just squeezes Saber’s hand and then straightens his back.

“Cú Chulainn,” he starts, “is what you may call me, and all variations thereof.”

Unintentional thought it might be, Saber’s grip on Cú Chulainn’s hand tightens enough that he’s grateful he’s still wearing his gauntlets, otherwise he’s sure he would’ve pierced skin, and he has to bite his own lip to stop himself from melting into the warm sensation that floods through him, the magic in his blood singing louder than a songbird.

“Well?” Cú asks, a cheeky smile on his face.

“Well what?” Saber asks back.

Cú looks down at where their hands are still joined and Saber quickly snatches his own right back, scowling at himself for indulging.

“Does this mean I can finally call you Diarmuid without you scrunching your face up or?”

“Sure,” he agrees, an automatic response from all the time Fionn had drilled social politeness into his brain, and then, “I don’t scrunch my face up!”

“You do,” Cú tells him. “It’s like looking at a rabbit.”

“A ra -!?” As if proving his point, Diarmuid’s face scrunches up into a cringe and he reaches out to smother Cú’s mouth before he can utter another sound. “Shut up,” he hisses and Cú’s eyes squint from the smile hidden behind a gauntlet.

“You’re impossible,” Diarmuid says.

“You love me,” Cú grins, smug as ever because he knows he’s right. Diarmuid wouldn’t have let him come along if he didn’t.

At least he’s not angry anymore. As attractive as he looked with fire in his hands, Diarmuid much prefers the laid back Caster to the one who was willing to burn down an entire town just because they accused Diarmuid of being a heartless monster who’d eat their children. In all honesty it’s not even one of the worst things humans have ever said about him, so he really doesn’t understand why Cú took it so personally. 

With Fionn, at least, he can understand the emotional response since they’ve been friends their whole lives, and any slight against one of them is a natural slight against the other. 

Trying to figure out Cú’s reasoning is a lot harder though, and it leads to more headaches than he’d like, so he chooses not to, and asking outright feels like it’d just set Cú’s anger off again. 

As if reading his mind, Cú says, “so much for not changing the subject, huh?”

Diarmuid shrugs. “I didn’t want you staying angry either, so it was a lose-lose either way. I just picked the lesser of two evils.”

Cú gives him a strange look - something he’s fond of doing - and then gets on his knees so that they’re nose to nose, and Diarmuid reflexively stiffens at the spatial intrusion. “They’re wrong,” he says, voice actually cracking, and Diarmuid has no fucking idea how he’s supposed to interpret this. Cú opens his mouth as if to say something else, closes it again, shakes his head, and quietly murmurs, “you deserve better than what they give you, is all.” 

His breath hitches in his throat, an emotion he can’t describe making his eyes widen and his chest hurt, and then he blinks and Cú is back on the other side of the fire, finally sewing up the tears in his clothes with an irritated click of his teeth. 

“ _Oh._ ”

**Author's Note:**

> There's a lil HC slipped in here about Cú's eyes so yeah my HC is that he has seven "rings" in each iris (like the shinigami from Black Butler lol) as a nice little nod to the Ulster stories that described as either having seven eyes or seven irises


End file.
